Do you struggle to make your cellular energy unit engaging for students? I have, too!

Photosynthesis and cellular respiration lab experiments can be tough to create because these cellular energy concepts are abstract and can be difficult for students to understand. Rather than just drilling them on molecular pathways and chemical equations, I’ve always tried to incorporate labs and activities to bring these concepts to life. I’ve seen some other photosynthesis and respiration labs, but they can be tricky and often frustrating for students. Instead, in planning my photosynthesis and cellular respiration unit, I’ve relied on some tried-and-true labs that are easy and inexpensive.

Photosynthesis Lab: Observing Stomata

This lab is more of a plant anatomy investigation, but it lends itself well to a discussion of photosynthesis, too. Students can use inexpensive materials (clear nail polish, clear tape, and a leaf) to make a microscope slide that allows them to observe the stomata of the leaf. The stomata are responsible for the gas exchanges required by the photosynthesis and cellular respiration processes. The guard cells on either side of the stoma opening are regulated by turgor pressure, so this is a great link between the concept of osmosis and photosynthesis. I usually do a quick discussion or exit ticket so students can explain which gases enter and leave through the stoma and how the available water regulates this gas exchange. Quick and easy, but it will amaze your students! You can see a video demonstration of this photosynthesis lab on my YouTube channel.

Looking to include other plant anatomy activities in your course? You might be interested in my post on incorporating plants into your Biology class.

Cellular Respiration Lab: “Barf” Bags

Barf bags are arguably one of my favorite activities during the first half of the Biology course.

These are unbelievably simple and I promise your students will remember them for years to come. By adding cereal, yeast, and warm water to a zipper bag, your students can see fermentation at work- all the way up to the point at which the bag pops! Although I don’t use formal lab reports often, there are a lot of variables that can be changed in this lab if you’d like to make it a true student-directed lab. The type of cereal, amount of each ingredient, and temperature of water all play a role in the amount of carbon dioxide being produced, so students can alter these variables to test which makes the biggest change in the alcoholic fermentation process. You can even grab my Barf Bag Lab for free in my Teachers Pay Teachers store.

Photosynthesis Lab: Leaf Chromatography

Leaf chromatography is an experiment that allows students to see the pigments hidden inside a leaf. The primary pigment inside a leaf is chlorophyll, which is responsible for the production of food through photosynthesis. When leaves change color in the autumn, the chlorophyll breaks down revealing the other pigments that remain. Photosynthesis is often taught in the autumn, which makes this lab perfect so students can teach their friends and families about seasonal color changes. If this experiment fits well into your course, you can use this free set of leaf chromatography instructions.

Cellular energy labs for virtual students are a little harder to find, but here are a few:

• Photosynthesis lab simulation from Biology Corner
• Photosynthesis interactive from HHMI
• Cellular Respiration Lab from Biology Corner
• Cell Energy Simulation from Biology Simulations

Linking Photosynthesis & Respiration: The BTB Lab

This lab requires a few more specific pieces of equipment, so I’m not counting it as an “inexpensive lab”, but if you have access to the supplies, it’s the perfect way to show the connection between the processes of photosynthesis and cellular respiration. Students start with a beaker of diluted bromothymol blue (BTB), which is a pH indicator. By blowing carbon dioxide into the BTB solution, they can change the indicator to green because carbon dioxide mixed with water creates carbonic acid. Adding an aquatic plant to the solution can remove the carbon dioxide, returning the BTB to blue. Students test this by using plants both in light and dark conditions to show the necessity of light in the photosynthesis process.

If you have a day or two to complete this lab activity, you won’t be sorry! Find a pre-made set of lab instructions in my TpT store.

Photosynthesis, cellular respiration, and fermentation are difficult and sometimes abstract concepts for students. I hope these lab ideas give them some opportunity to interact with these challenging but essential life processes. If you use some of these photosynthesis and cellular respiration lab ideas to get your students engaged with these tough concepts, I’d love to hear about it!